Formulation of Thermally Cured Organic-Inorganic Superhydrophilic Coating for Antifogging Optical Application

Abstract

Formation of coatings with combined properties of being superhydrophilic/superhydrophobic are of immense applications in the field of optics. In our present work, we have developed a transparent, organic/inorganic hybrid coating by mixing appropriate ratios of organic silanol coupling agents and monoacrylates to impart strong adhesion to the substrate, and inorganic components comprising of a hybrid mixture of silica-titania, and certain vinyl components as well as hydrophilic surfactants for improved antifogging behavior. Polycarbonate lens or glass slides, as substrates were dip coated into the hybrid precursor solution at a suitable withdrawal rate of 5 cm/min to form uniform and crack free film of thickness 458 nm. The sequential process of drying of the coated films involved thermal curing at varied temperature and time in the presence of an appropriate thermal initiator, dicumyl peroxide. The surface chemistry and thermal behavior along with the superhydrophilicty and fogging behavior of the coated substrates were assessed by respective ATR-IR, ²⁹Si NMR, TGA/DSC analysis and AFM measurements. The remarkabale observation was that the composite of organic-inorganic mixture exhibited desired properties of being superhydrophilic as well as antifogging on the substrate by curing at appropriate temperature of 50°C for 24 hr and 120°C for 8 hr, respectively.